Water Tables Falling

Water is vital to life. To many of us, it is within reach of a faucet, but for many others it is not. And it is fast becoming a scarce resource. As I note in Plan B 2.0 ), more than half the world's people live in countries where water tables are falling.

The U.S. embassy in Beijing reports that Chinese wheat farmers in some areas are now pumping from a depth of 300 meters, or nearly 1,000 feet. Pumping water from this far down raises pumping costs so high that farmers are often forced to abandon irrigation and return to less productive dryland farming. A World Bank study indicates that China is overpumping three river basins in the north--the Hai, which flows through Beijing and Tianjin; the Yellow; and the Huai, the next river south of the Yellow. Since it takes 1,000 tons of water to produce one ton of grain, the shortfall in the Hai basin of nearly 40 billion tons of water per year (1 ton equals 1 cubic meter) means that when the aquifer is depleted, the grain harvest will drop by 40 million tons--enough to feed 120 million Chinese. In India, water shortages are particularly serious simply because the margin between actual food consumption and survival is so precarious. In a survey of India's water situation, Fred Pearce reported in New Scientist that the 21 million wells drilled are lowering water tables in most of the country. In North Gujarat, the water table is falling by 6 meters (20 feet) per year. In Tamil Nadu, a state with more than 62 million people in southern India, wells are going dry almost everywhere and falling water tables have dried up 95 percent of the wells owned by small farmers, reducing the irrigated area in the state by half over the last decade.

As water tables fall, well drillers are using modified oil-drilling technology to reach water, going as deep as 1,000 meters in some locations. In communities where underground water sources have dried up entirely, all agriculture is rain-fed and drinking water is trucked in. Tushaar Shah, who heads the International Water Management Institute's groundwater station in Gujarat, says of India's water situation, "When the balloon bursts, untold anarchy will be the lot of rural India."

In the United States, the U.S. Department of Agriculture reports that in parts of Texas, Oklahoma, and Kansas--three leading grain-producing states--the underground water table has dropped by more than 30 meters (100 feet). As a result, wells have gone dry on thousands of farms in the southern Great Plains. Although this mining of underground water is taking a toll on U.S. grain production, irrigated land accounts for only one fifth of the U.S. grain harvest, compared with close to three fifths of the harvest in India and four fifths in China.

Pakistan, a country with 158 million people that is growing by 3 million per year, is also mining its underground water. In the Pakistani part of the fertile Punjab plain, the drop in water tables appears to be similar to that in India. Observation wells near the twin cities of Islamabad and Rawalpindi show a fall in the water table between 1982 and 2000 that ranges from 1 to nearly 2 meters a year.

In the province of Baluchistan, water tables around the capital, Quetta, are falling by 3.5 meters per year. Richard Garstang, a water expert with the World Wildlife Fund and a participant in a study of Pakistan's water situation, said in 2001 that "within 15 years Quetta will run out of water if the current consumption rate continues."

Iran, a country of 70 million people, is overpumping its aquifers by an average of 5 billion tons of water per year, the water equivalent of one third of its annual grain harvest. Under the small but agriculturally rich Chenaran Plain in northeastern Iran, the water table was falling by 2.8 meters a year in the late 1990s. New wells being drilled both for irrigation and to supply the nearby city of Mashad are responsible. Villages in eastern Iran are being abandoned as wells go dry, generating a flow of "water refugees."

Saudi Arabia, a country of 25 million people, is as water-poor as it is oil-rich. Relying heavily on subsidies, it developed an extensive irrigated agriculture based largely on its deep fossil aquifer. After several years of using oil money to support wheat prices at five times the world market level, the government was forced to face fiscal reality and cut the subsidies. Its wheat harvest dropped from a high of 4 million tons in 1992 to some 2 million tons in 2005. Some Saudi farmers are now pumping water from wells that are 1,200 meters deep (nearly four fifths of a mile).

In neighboring Yemen, a nation of 21 million, the water table under most of the country is falling by roughly 2 meters a year as water use outstrips the sustainable yield of aquifers. In western Yemen's Sana'a Basin, the estimated annual water extraction of 224 million tons exceeds the annual recharge of 42 million tons by a factor of five, dropping the water table 6 meters per year. World Bank projections indicate the Sana'a Basin--site of the national capital, Sana'a, and home to 2 million people--will be pumped dry by 2010.

In the search for water, the Yemeni government has drilled test wells in the basin that are 2 kilometers (1.2 miles) deep--depths normally associated with the oil industry--but they have failed to find water. Yemen must soon decide whether to bring water to Sana'a, possibly by pipeline from coastal desalting plants, if it can afford it, or to relocate the capital. Either alternative will be costly and potentially traumatic.

Israel, even though it is a pioneer in raising irrigation water productivity, is depleting both of its principal aquifers--the coastal aquifer and the mountain aquifer that it shares with Palestinians. Israel's population, whose growth is fueled by both natural increase and immigration, is outgrowing its water supply. Conflicts between Israelis and Palestinians over the allocation of water in the latter area are ongoing. Because of severe water shortages, Israel has banned the irrigation of wheat.

In Mexico--home to a population of 107 million that is projected to reach 140 million by 2050--the demand for water is outstripping supply. Mexico City's water problems are well known. Rural areas are also suffering. For example, in the agricultural state of Guanajuato, the water table is falling by 2 meters or more a year. At the national level, 51 percent of all the water extracted from underground is from aquifers that are being overpumped.

Since the overpumping of aquifers is occurring in many countries more or less simultaneously, the depletion of aquifers and the resulting harvest cutbacks could come at roughly the same time. And the accelerating depletion of aquifers means this day may come soon, creating potentially unmanageable food scarcity.